Hemoglobin (Hb) A2, Quantitative

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Turnaround Time: 2 - 5 days
CPT Code:


Test Type: 1 mL Whole blood
Stability Time:



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Reference Range:



<7 mo

Not established

7 mo to 1 y

1.9% to 2.8%

≥2 y

1.8% to 3.2%


Investigate for hemolytic anemia, hemoglobinopathies, and thalassemia.

Blood transfusion prior to hemoglobin analysis may cause inconsistent interpretation.

Hemoglobin A2 levels have special application to the diagnosis of β-thalassemia trait, which may be present even though peripheral blood smear is normal. (This reflects the underlying genetic spectrum of β-thalassemia, which in reality is a complex of 20 to 30 distinct conditions.) The microcytosis and other morphologic changes of beta-thalassemia trait must be differentiated from iron deficiency. Low MCV may include the majority of β-thalassemia trait patients but does not differentiate iron deficient individuals. Low Hb A2 levels occur in untreated iron deficiency. If the β-thalassemia is associated with iron deficiency, the Hb A2 level falls, making the differentiation even more difficult (corrected after iron therapy).1 The most definitive evidence for presence of β-thalassemia trait is genetic (family study). Offspring of a person with thalassemia major will have beta-thalassemia trait. Hb A2 may be increased in megaloblastic anemia and may be decreased in sideroblastic anemia, Hb H disease, and erythroleukemia.

1. Wasi P, Disthasongchan P, Na-Nakorn S. The effect of iron deficiency on the levels of hemoglobins A2 and E. J Lab Clin Med. 1968 Jan; 71(1):85-91. PubMed 5635011

Collection Details:

Patient Preparation:

Fasting or fluid restriction is not necessary.

Collection Instructions:

Specify on the request form the patient's race or ethnic origin (if known) as well as the date of any transfusions administered within the preceding three months.

Lavender-top (EDTA) tube.

To avoid delays in turnaround time, please submit a separate lavender-top tube for each test requiring a lavender-top.

Refrigerate at 2°C to 8°C.